Apple CEO Tim Cook toured an Austin, TX facility that manufactures the new Mac Pro, and his crew predictably used the visit as a photo op, snapping an image of Cook peering over the shoulder of a worker soldering something and posting it on Twitter.

“Watching the Mac Pro come together in Austin yesterday,thanks to a team loaded with American manufacturing expertise,” reads the Twitter post.

However, a number of people noticed something humorously off about the photo: The computers in the background appear to be running Windows. Thus, it would seem that Apple is using Windows software to help create its Mac Pro machines.

It’s more of a simple PR gaff than anything else, but it’s still funny any time a company is spotted using a competitor’s product--especially when the CEO of one of those companies is in the shot.